I'd go 70D if it were me, with not much need for debate. While the 6D has low noise, the lack of swivel screen and DPAF on 6D makes 70D more video-friendly. In other words, while the 6D has a lower noise sensor most other things about the camera for video are a disadvantage compared to the 70D. Also, I've heard the 6D has moire issues w/ video.

One thing to consider, neither one has a headphone jack unfortunately to monitor audio on videos - likely we will have to wait for the 7D2 for that in the pricerange w/ articulating screen.

If you're going to do videos like demonstration and the like, I would hands-down go with the 70D. Unless you have a friend, a third arm, or you're an octopus, you'll definitely need the auto-focus of the 70D when you hold up items to show the viewers/camera. It'll be hard to focus the camera with one hand and demonstrate a phone or something with another. Also, the low light powers of the 6D are of course better, but you don't need anything extreme indoors, especially with sufficient lighting. I'm sure you wouldn't be shooting at night with your small light on anyhow and even then with a 6D, wouldn't look that great.

I'd use a 70D and external sound recorder. I believe the 70D has time coding, so its easy to synch the sound, and it will be much better.With the autofocus capability, when you hold your iphone up to the lens for a close up, it will snap into sharp focus without needing a focus puller. If you do have someone to pull focus, he only needs to touch the item on the touch screen and the focus will shift to it. For informal video that's easy to do, its a big step forward.

6d can shot raw video and all the other perks of ML. However, I have heard the noise on the 6d is terrible. I've seen comparison videos and it really isn't as bad as people say, but its not a good thing. I think you're better off getting a used 5dii. Heard only good things about the 70d. I'd say wait for the new cameras to come out or 70d.